The Facebook in-app browser has strict policies on playing media over SSL encrypted website sites with mixed content. If it detects the site is HTTPS and the shoutcast media stream is non-SSL, it does not play the audio. It will only play the audio over SSL in that case.

The strangest thing I am seeing is that the streaming.shoutcast.com/xxx stream is encrypted by SSL only in the Chrome Beta mobile browser. However, it is non-SSL in all other desktop browsers and other mobile browsers including FB in-app.